Prostaglandins (PG) are produced abundantly in the site of inflammation and involved in progress of inflammation. Prostaglandin production is initiated with the release of arachidonic acid from membrane glycerophospholipid by phospholipase A2, and the arachidonic acid is then converted into prostaglandin H2 (PGH2) by cyclooxygenase (COX). PGH2 is converted into prostaglandins including prostaglandin E2 (PGE2), prostaglandin F2α (PGF2α), prostaglandin D2 (PGD2), prostaglandin 12 (PGI2), and thromboxane A2 (TXA2). These prostaglandins are known to have various physiological or pathophysiological activities, including inflammation-inducing effect. Especially, PGE2 is known as an inflammatory inducer in acute and chronic inflammations and further known to induce pyrexia and hyperpathia. Non-steroidal anti-inflammatory drugs (NSAIDs) and selective COX-2 inhibitors have anti-inflammatory effect via reduced production of PGE2 based on their COX-1 and/or COX-2 inhibitory effect. PGE2 synthase (PGES) catalyzes the final step of the synthetic pathway of PGE2, which is an inflammatory mediator. To date, three subtypes of PGES, microsomal prostaglandin E synthase-1 (mPGES-1) (for example, Jakobsson et al., Proc. Natl. Acad. Sci. USA, 1999, 96, 7220-7225), mPGES-2 (for example, Tanikawa et al., Biochem. Biophys. Res. Commun., 2002, 291, 884-889) and cytosolic prostaglandin synthase (cPGES) (for example, Tanioka et al., J. Biol. Chem., 2000, 275, 32775-32782) are known. Among these, mPGES-1, in the same manner as COX-2, is primarily induced during inflammation and plays a major part in PGE2 production in inflammatory lesion. On the other hand, cPGES is constitutively expressed PGES and coupled to COX-1 to play a part in basal PGE2 production (for example, Murakami et al., J. Biol. Chem., 2000, 275, 32783-32792). As to mPGES-2, it is a subject of controversy as there is a report that it can be coupled to both COX isoforms. The studies in mPGES-1-deficient mouse suggest that mPGES-1 contributes to pathological progress in various inflammation models, such as acetic acid writhing model (e.g., Kamei et al., J. Biol. Chem., 2004, 279, 33684-33695), arthritis model (e.g., Kamei et al., J. Biol. Chem., 2004, 279, 33684-33695 and Kojima et al., J. Immunol., 2008, 108, 3861-3868), multiple sclerosis model (e.g., Kimura et al., Proc. Natl. Acad. Sci. USA, 2000, 106, 21807-21812), and fever model (e.g., Engblom et al., Nat. Neurosci., 2003, 6, 1137-1138). Also, mPGES-1 inhibitors specifically inhibit COX-2-dependent PGE2 production, and therefore, they are expected to reduce various side effects, compared with NSAIDs or COX-2 inhibitors. It is believed that elevated risk of cardiovascular events by COX-2 inhibitors is attributed to enhanced coagulation system and vasoconstriction via inhibited COX-2-dependent PGI2 production (e.g., Foudi et al., Cardiovasc. Res., 2009, 81, 269-277). In contrast, mPGES-1 inhibitors are believed not to increase the risk of cardiovascular events, which is a problem with COX-2 inhibitors, since they do not inhibit PGI2 production (e.g., Cheng et al., J. Clin. Invest., 2006, 116, 1391-1399). mPGES-1 inhibitors are expected to serve as a safe anti-inflammatory agent by inhibiting only PGE2 production, which participates in inflammation. Thus, a pharmaceutical agent which is able to inhibit mPGES-1, and reduce PGE2 production is useful in the treatment or prevention of a disease, such as an inflammatory disease in which mPGES-1 participates. mPGES-1 inhibitors have been disclosed in the patent applications by NovaSAID AB (WO2009/103778 and US2010/0324086) and Boehringer Ingelheim International GmbH (WO2011/048004).